Abstract

Residual dye contents in textile wastewater are one of the most important sources of environmental pollution because of both their visibility and toxicity. The use of metallic particles has been shown to be an effective, low-cost method for degradation of many contaminating compounds. In this work, we analyze the efficiency of manganese (Mn)- aluminium (Al) metallic powders for degrading azo dyes, which are one of the most important families of colorants utilized by the textile industry. Using a ball-milling process under an Ar gas atmosphere, the powder samples were milled at a speed of 500 rpm. Three different powders were obtained by milling for a total time of 20, 30, and 60 hours. The morphology, particle size distribution and chemical composition of the Mn-Al powders was characterized by scanning electron microscope (SEM) and energy dispersive X-ray microanalysis system (EDX). Here we present new results obtained on the decolorization of Orange II azo dye aqueous solutions. The decolorization process was monitored by ultraviolet-visible (UV) spectrophotometry showing fast kinetics, with reaction times among the shortest if compared to the results reported using other materials. The activation energy was determined to be 43.9 kJ mol-1. Various parameters such as pH, initial dye concentration, contact time and different temperatures were studied in terms of their effect on the reaction progress. Finally, we determined the minimum dosage of metallic particles in order to achieve 100% decolorization.